Withanolides are ergostane-type steroids that have been isolated mainly from plants of the family Solonaceae and, specifically, from genera Withania, Duralia, Datura, Jaborosa, Physalis, Deprea and Nicandria. Throughout the world there are many folk applications of these plants. Their extracts, for example, are used in the treatment of asthma, hepatic diseases, several inflammatory processes and cancer, and even as a hypnotic drug. Withjardin A, B, C and D and derivatives thereof are withanolides isolated from leaves and stems of Deprea orinocensis and can be used as immunomodulators of the immune system (see Patent U.S. Pat. No. 5,681,950).
Physalins are steroidal constituents of Physalis spp. which belongs to the Solanaceae family and are characterized by their modified ergostane-type framework, being 16,24-cyclo-13,14-secosteroids. The most studied species are: P. angulata, P. alkekengi var francheti, P. ixocarpa, P. laninfolia, P. minima, P. peruviana, P. phyladelphia, P. pubescens and P. viscosa. As a result of their polyfunctional structures, physalins can be classified as the most advanced group in terms of the biogenetic oxidation level among withasteroids.
Physalins are normally present at levels of 30 to 500 ppm in root and epigeal parts of Physalis species. P. angulata is an annual herb widely grown through the North and Northeast of Brazil (Braga, R., Plantas do Nordeste, especialmente do Ceará, Mossoró, Brasil, ESAM, 540, 1976) and is popularly known as “Bate-Testa”, “Bucho de Rã”, “Mata-Fome”, “Juá” or “Juá de Capote” and more frequently, “Camapú” (Pio Corrêa, Dicionário das Plantas úteis do Brasil e das exóticas cultivadas, R10 de Janeiro, Min. da Agricultura, Vol. I, pp. 10, 1962).
Crude extracts from Physalis species are reported to have been used in indigenous medicine systems. It is also mentioned by Sanchez et al (Sanchez, E. G., Silva, M. T. G., Ribeiro, I. M., Tomassini, T. C. B., Evolutions of the antibacterial activity of Physalis angulata L., in Abstracts of the 1st Congress of Pharmaceuticals Sciences, Ribeirao Preto, S. Paulo, Brasil,—Index. Bolletino Chimico Farmaceutico, Vol. 136, pp. 154, 1997) that Physalis extracts and their isolated constituents exhibit biological activity, including the anti-bacterial effect of P. angulata extracts from root, leaf and stem-bark.
Chiang et al (Chiang, H. C., Jaw, S. M., Chen, C. F. e Kan, W. S., Anticancer Research 12, 837, 1992.) demonstrated that physalins A, D, F e L extracted from Physalis species have been shown to be active against human tumors like hepatoma, cervix uteri, lung and colon cells in vivo and in vitro tests.
As described in U.S. Pat. No. 5,135,746 the use of active compounds extracted from plants with pharmacological activity have been used for the prophylactic and therapeutic treatment of protozoal diseases, such as malaria and amebic dysentery from old times.
Conventionally used agents for the treatment of protozoal diseases caused by the genera Trypanosoma and Leishmania are quite unsuitable for widespread use due to its unpleasant side-effects, primarily nausea, vomiting and allergic reactions, and to some cases of drug resistance.
Chagas Disease, caused by infection with the parasite Trypanosoma cruzi, is responsible for the infection of 16–18 million people. Moreover, some 100 million people—a quarter of all the inhabitants of Latin America—are at risk of contracting the disease (Tropical Disease Research, World Health Organization, pp. 125–133, Geneva, 1995).
The disease usually begins as an acute infection in childhood, which may last up to two months, followed by a slow, chronic inflammatory process, which in around a quarter of those infected damages the autonomous nervous tissues of the heart, a condition which in turn may cause heart failure and premature death in mild life.
Unfortunately, no treatment is available for the chronic forms of the disease. Nifurtimox, a nitrofuran derivative, and benzinidazole, a nitroimidazole, are oral synthetic drugs used in acute cases, but their efficacy varies considerably from place to place, perhaps due to variation in parasite strains. The drugs must be taken daily for long periods. Both drugs can produce unpleasant side-effects, allergic reactions and nauseas.
Plant extracts and/or its isolated components may be an alternative for commercial drugs used for treating Chagas Disease. As an example of this approach, it may be cited the document U.S. Pat. No. 5,290,553 which describes the use of purified extracts and alkaloids from Picralima nitida and Dorstenia multiradiata in mammals infected with Trypanosoma brucei brucei. 
Another example of medicinal plants with trypanocidal activity was described by Freiburghaus et al (Freiburghaus, F., Kaminsky, R., Nkunya, M., H., H., e Brun, R., “Evaluation of African medicinal plants for their in vitro trypanocidal activity”, J. Of Ethnopharmacology, 55, pp. 1–11, 1996). The authors screened 24 plant extracts commonly used in african traditional medicine for the treatment of Human African trypanosomiasis (sleeping sickness) caused by Trypanosoma brucei rhodesiense. The most active extracts with IC50 values below 1 μg/ml were derived from Annona senegalensis, Bussea occidentalis and Physalis angulata. Compared to IC50 values of commonly used trypanocidal drugs, e.g. suramin at a concentration of 10.7 ng/ml, the values even for active extracts were high. However, since the crude plant extracts used are mixtures of various compounds, purification or active extracts might result in a considerable increase in activity.
It is important to emphasize that neither these plant extracts nor their contents were tested against T. cruzi, the causative agent of Chagas Disease.
When untreated sleeping sickness eventually gives no respite from suffering, day or night, and ends in death (WHO, 1994). It affects 250 000 to 300 000 people per year. The causative agents are Trypanosoma brucei rhodesiense in East Africa and Trypanosoma brucei gambiense in West and Central Africa.
The available drugs used in the treatment of sleeping sickness are suramin, pentamidine, melarsoprol and difluoromethylornithine (DEMO) and may cause severe side effects. Moreover, these drugs do not present any effect against Trypanosoma cruzi and, consequently, are not used in the treatment of Chagas Disease.
Consistently, both parasites and drugs used for the treatment of Chagas Disease and Sleeping Sickness are distinct. In fact, different species or strains may cause different diseases. So, it is unpredictable to forsee that the efficacy of a medicament used to treat Sleeping Sickness remain the same when dealing with Chagas Disease.
Infections due to protozoa of the genus Leishmania are also a threatened world-wide health problem with high endemicity in developing countries. Leishmania infections are zoonosis globally affecting individuals. Approximately 400 million people within 80 countries are at risk of contracting the disease, 12 million are already infected in the world and the disease growing rate being about 600 thousand new cases a year (WHO, 1994). The pathological effects of the disease are complex and manifests itself as various forms ranging from self-healing cutaneous lesions, post-kala-azar dermal leishmaniasis, disfiguring mucocutaneous and diffuse cutaneous diseases to fatal systemic infection caused by visceral leishmaniasis (Kala azar).
Leishmanias are digenetic protozoas which invade the macrophages of the host and have a complex life cycle based on two different hosts and two distinct evolution cycle. The promastigote form is elongated having a free anterior flagellum which lives in a vector while the amastigote has an ovoid shape without free flagellum and may be found intracellularly in vertebrate hosts. The vector is a group of more than 50 species and sub-species of insects belonging to the genera Lutzomyia, occuring largely in the Americas, and Phlebotomus which may be found elsewhere.
At the present time, the clinical drug intervention is limited primarily to the use of pentavalent antimonials, sodium stibogluconate and N-methylglucamine antimonate, and secondarily to amphotericin or pentamidine. These antileishmanials require parenteral administration with clinical supervision or hospitalization during treatment because of the severity of possible toxic side-effects that include cardiac and/or renal failure.
The treatment with the aforementioned agents is not consistently effective, particularly for the most virulent leishmanial disease forms. The World Health Organization has reported large scale resistance of kala-azar to pentavalent antimonials which are the preferred chemotherapy for the treatment of the most forms of leishmanial disease (TDR News. December. 1990). In some endemic regions, it has been observed that prolonged medication (22 months or more) with pentavalent antimonials is required to effect a clinical cure. However, long term therapy with this class of drugs is not usually justifiable due to the mentioned cardiac and renal toxicity of pentavalent antimonials.
In this context, a great effort has been made in order to identify natural products with leishmanial activity. Berberine, an isoquinolinic alkaloid, has been shown to possess significant leishmanicidal activity. This substance can be found in the Berberis aristat specie and is largely used in popular medicine for the treatment of leishmaniasis and other diseases caused by protozoans. According to Iwu et al (Iwu, M. M., Jackson, J. E. and Schuster, B. G. (1994). “Medicinal plants in the fight against Leishmaniasis. Parasitol. Today. 10(2): 65–68), experiments proved that this drug possess a great leishmanicidal activity, in vivo and in vitro, against lots of Leishmania species.
U.S. Pat. No. 5,290,553 describes alkaloid extracts from seeds, fruit-rind and stem-bark and new isolated alkaloids from Picralima nitida, and alkaloid extracts from seeds, fruit-rind and stem-bark of plants selected from the group consisting of Gongronema latifolia, Rothmania withfieldii and Desmodium gangeticum used for the treatment of protozoal diseases including leishmanial infections in mammals.
Concerning to auto-immune diseases, such as SLE (systemic lupus erythematous), rheumatoid arthritis, auto-immune thyroiditis, Sjøgren's syndrome, idiopathic thrombocytopenic purpura and haemolytic anaemia, many treating substances have been proposed. In U.S. Pat. No. 4,701,450, it is described the use of pharmaceutical preparations based on steroids, particularly oestrene derivatives, as immunomodulators. U.S. Pat. No. 5,276,013 refers to compositions for treating the auto-immune disease systemic lupus erythematosus, the compositions being related to conjugates of biologically stable valency platform molecules such as polymers, preferably copolymers of glutamic acid and D-lysine or polyethylene glicol and certain polynucleotides that have been found to be effective for inducing tolerance to self-antigens involved in SLE.
Some individuals acquire auto-immune diseases due to failure in immune tolerance mechanism which may be defined as a permanent form of immunesupression that keeps individuals from reacting with their own tissues.
Auto-immune diseases are typically treated with broad spectrum, nonspecific immunosuppressants such as cyclophosphamide or prednisone. But these drugs cause deleterious side-effects related with suppression of all aspects of the immune system, thus causing the inhibition of its essential and beneficial functions. Consequently, these drugs must be administered with extreme caution and are not always appropriate to manage the disease on a continuing basis. In fact, severely immunosuppressed individuals by drug treatment are at risk for other complications, especially infectious diseases.
Accordingly, there is a great need for a more effective and mild anti-parasite drug without the disadvantages of the available chemotherapeutic agents which are toxic and drug resistance are becoming widespread. There is also a need for immunomodulators capable of reestablishing immune tolerance to the autoantigens without affecting the normal functions of the immune system. Such an improved drug may be used in a lower concentration and must provide a higher survival inhibition. This can be accomplished by using plant extracts and more particularly its steroid derivatives components.